Herbicidally active compounds are used to control or modify the growth of plants. Herbicidal compositions containing one or more active herbicidal compounds can be formulated and applied in a variety of ways. The object of a particular formulation is to apply the herbicidal compound(s) to an area where plant growth control is desired in a convenient, safe and effective way.
The choice of formulation and mode of application for any given herbicidal compound may affect its activity, and selection must be made accordingly. Herbicidal compositions may thus be formulated as granules, as wettable powders, as emulsifiable concentrates, as powders or dusts, as flowables, as solutions, as suspensions or emulsions, or as controlled release forms such as microcapsules.
Wettable powders are in the form of finely divided particles which disperse readily in water or other liquid carriers. The particles contain the active ingredient retained in a solid matrix or the active ingredient can be commingled with the solid matrix particles. Typical solid matrices include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic solids. Wettable powders normally contain about 5% to about 95% of the active ingredient plus a small amount of wetting, dispersing, or emulsifying agent.
Emulsifiable concentrates are homogeneous liquid compositions dispersible in water or other liquid, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthas, isophorone and other non-volatile organic solvents. In use, these concentrates are dispersed in water or other liquid and normally are applied as a spray to the area to be treated. The amount of active ingredient may range from about 0.5% to about 95% of the concentrate.
Granular formulations include both extrudates and relatively coarse particles, and are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, attapulgite clay, bentonite clays, montmorillonite clay, vermiculite, perlite and other organic or inorganic materials which absorb or which can be coated with the active compound. Granular formulations normally contain about 5% to about 25% active ingredients which may include surface-active agents such as heavy aromatic naphthas, kerosene and other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins.
Dusts are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers.
Microcapsules and encapsulated granules are typical controlled release formulations. Microcapsules are typically droplets of the active material enclosed in an inert porous shell which allows escape of the enclosed material to the surroundings at controlled rates. Encapsulated droplets are typically about 1 to 50 microns in diameter. The enclosed liquid typically constitutes about 50 to 95% of the weight of the capsule, and may include solvent in addition to the active compound. Encapsulated granules are generally porous granules with porous membranes sealing the granule pore openings, retaining the active species in liquid form inside the granule pores. Granules typically range from 1 millimeter to 1 centimeter, preferably 1 to 2 millimeters in diameter. Granules are formed by extrusion, agglomeration or prilling, or are naturally occurring. Examples of such materials are vermiculite, sintered clay, kaolin, attapulgite clay, sawdust and granular carbon. Shell or membrane materials include natural and synthetic rubbers, cellulosic materials, styrene-butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, polyureas, polyurethanes and starch xanthates.
Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a solvent in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprayers, wherein the active ingredient is dispersed in a finely-divided form as a result of atomization and vaporization of a low boiling dispersant solvent carrier, may also be used.
Although dusts and granular formulations are used for the application of some herbicidal compounds, drift due to wind is a problem with such dry formulations and, consequently, liquid formulations are preferred. Liquid formulations are also advantageous in that they permit the "tank mixing" of two or more agriculturally active formulations at the grower site.
The discovery of herbicidal dione compounds having the general formula (I): ##STR2## wherein R.sup.1, R.sup.2, X and Z have the meanings set forth hereinafter, has resulted in considerable field testing of these compounds alone and in combination with other agriculturally active compounds for various uses worldwide.
These herbicidal dione compounds have the disadvantage that in water and other solvents (in which there is appreciable solubility) they can undergo decomposition. This decomposition occurs at such a rate that the use of these herbicidal dione compounds in aqueous herbicidal formulations or formulations containing an organic solvent or liquid co-herbicide is impractical, unless the formulation is prepared immediately or within a short period of time prior to use.
It is, therefore, an object of this invention to provide metal chelates of the herbicidal dione compounds of formula (I) which are chemically stable for long periods of time under normal as well as extreme temperature conditions. Another object of the present invention is to provide liquid herbicidal formulations based on the herbicidal dione compounds of formula (I) and water, an organic solvent or a liquid co-herbicide, which formulations are chemically stable.